This invention relates in general to synchronizer assemblies for manually operable vehicle transmissions and in particular to a split pin structure for supporting a movable clutch collar in such a transmission synchronizer assembly.
In most vehicles, a transmission is provided in the drive train between the engine and the driven wheels. As is well known, the transmission includes a plurality of gears which are selectively engaged to provide a plurality of speed reduction gear ratios between the input and the output thereof. One or more control members contained within the transmission are moved by a driver of the vehicle throughout a plurality of gear ratio positions for selecting the desired speed reduction. As a result, acceleration and deceleration of the vehicle can be achieved in a smooth and efficient manner.
In many transmissions, the control members are embodied as a plurality of clutch collars, each of which is movable between a neutral or non-gear engaging position and one or more gear engaging positions. Typically, each clutch collar includes a plurality of axially extending teeth which permit it to be splined onto a shaft contained within the transmission. As a result, the clutch collars are supported on the shaft for concurrent rotational movement, while permitting relative axial movement therebetween. A pair of gears are rotatably supported on the shaft on opposite sides of the clutch collar. Each of the gears is formed having a plurality of teeth which is complementary in size and shape to the plurality of teeth formed on the clutch collar. When the clutch collar is located in the neutral position, the plurality of teeth formed thereon does not engage the associated plurality of teeth formed on either of the adjacent gears. Therefore, no driving connection is provided between the shaft and either of such gears. When the clutch collar is moved axially toward one of the gears, the plurality of teeth formed thereon engages the associated plurality of teeth formed on that gear. Therefore, a driving connection is provided between the shaft and the selected gear.
As is well known in the art, the various gears and shafts contained within the transmission often rotate at different rotational speeds. If the clutch collar is moved from the neutral position to the gear engaging position when there is a significant difference between the respective rotational speeds of the clutch collar and the selected gear, undesirable clashing of the associated pluralities of teeth formed thereon will occur. In non-synchronized transmissions, the driver of the vehicle must use care and skill to operate the vehicle is such a manner as to prevent this from occurring. However, in some transmissions, the clutch collar is formed as part of a synchronizer assembly, which functions to automatically reduce the difference in the relative rotation speeds of the clutch collar and the selected gear when the clutch collar is axially moved as described above. Thus, in synchronized transmissions, the synchronizer assembly automatically minimizes the occurrence of this undesirable teeth clashing.
A typical transmission synchronizer assembly includes a pair of annular and co-axial friction races which are disposed on opposite sides of the clutch collar. The two friction races are rigidly fixed relative to one another in a spaced apart relationship, usually by a plurality of circumferentially spaced blocker pins. The clutch collar has a plurality of axially extending openings formed therethrough, through which the blocker pins extend. Thus, the clutch collar is supported between the two friction races for rotation therewith, yet can move axially relative thereto. The friction races are adapted to engage cooperating friction faces provided on each of the adjacent gears of the transmission before the clutch collar is moved to a gear engaging position so as to reduce the difference in the relative rotation speeds of the clutch collar and the selected gear.
Means are provided for releasably retaining the clutch collar in a central position between the two friction races. To accomplish this, it is known to provide a plurality of spring pins which extend axially between the two friction races. Typically, the spring pins are located circumferentially between adjacent ones of the blocker pins and extend through respective axially extending apertures formed through the clutch collar. Annular recesses are formed in the outer surfaces of the spring pins near the centers thereof. The recesses of the spring pins resiliently engage the clutch collar and thereby function to releasably retain the clutch collar in the center position between the two friction races.
A number of spring pin structures are known in the art for use in transmission synchronizers of this general type. Although known spring pins function satisfactorily, they have been found to be relatively expensive to manufacture and assemble. Known types of spring pins include flat stamped spring loaded members, spring loaded plungers, and split-pin members consisting of a pair of semi-cylindrical halves which are biased apart by separate resilient springs, such as leaf springs. The ends of these known spring pins have been mounted in recesses formed in the opposed, inwardly facing surfaces of the friction races, thereby necessitating expensive machining. Also, it has been found that the resilient spring structures contained within known spring pins are subject to fatigue. Thus, it would be desirable to provide an improved structure for a transmission synchronizer spring pin which is less expensive than known designs, and further is less subject to fatigue than conventional designs.